FM REUSE_ALV_GRID_DISPLAY - runtime error

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I get the following error when I use FM REUSE_ALV_GRID_DISPLAY:

"Field catalog not found".

I realize that it is looking for the parameter it_fieldcat but I don't remember ever passing that parameter before; it also says that it is optional. Below is my call to the FM. Does the addition of it_sort mean that I must pass it_fieldcat?